“You’re making the mistake of assuming these people are Christians. They may very well not be.”
No one knows who is in heaven for sure. Except for perhaps Seth, Enoch, Moses, Elijah, and Lazarus. The thief on the cross. Perhaps I have forgotten a handful.
The point is, the fact that Abraham, David, and Solomon sinned in this way doesn’t mean it is ok for us to do it.
They did a lot of other recorded sins, too, and we can’t copy those, either.
Like I said, you’re making the mistake of thinking these people are Christians. So they’re probably not too worried about how the God of Abraham defines sin.
Our preacher got asked that the other day about the mulitple wives, and why that seemed to be “okay” with God back then.
He pointed out some OT verses where it was NOT okay. But he also mentioned how God had bigger things for David (and the others) to work on first. Just like us. And, in spite of their (and our) flaws, God can still use us.